Bollinger Bands
Volatility bands placed above and below a moving average.
Full Definition
Bollinger Bands consist of a middle band (typically 20-period SMA) and upper/lower bands set at a specified number of standard deviations (usually 2) from the middle. Bands expand during high volatility and contract during low volatility. Price touching the bands can indicate overbought/oversold conditions, and band squeezes often precede breakouts.